Keying out Black

I am hoping to get some advice, I have a shot of a butterfly flying that in against a black background ( this back ground is not perfect but pretty close. I want to Key out the Black so i can have the butterfly fly across my AE graphic, what would be the best way to do this?

I seem to have left my cables for my drive at home so can not check it right now! It is archive so can not reshoot :-s Yet the butterfly is white and the body brown I was hoping I could get it to see black, maybe it was a hope too far.

This is basically the same as the Method Dave L. suggests and, therefore, has the same limitations (if there's no black in the butterfly, which seems unlikely) ... you can also an UnMult filter (like the free one from Red Giant that's primarily intended for use with older Lens Flares that don;t have premult capability built in).

It's hard to to day without seeing the image or the background you want it on, as well as the quality level you need, but in some instances a blend mode might even be sufficient for a quick shot.

Thank you all for your helped, It proved to be a hard one to do and as i am working on a tight dead line i have decited to animate a drawing of a butterfly instead. On that i have a new problem, the butterfly follows across a "s" shaped path I want this image to turn with the path rather than moving in an unnatural way. I have heard I can do this in a few clicks but unsure how.